Human Reproduction, Vol. 10, No. suppl_1, pp. 120-127, 1995
© 1995 European Society of Human Reproduction and Embryology
Genetics of abnormal human fertilization
The Center for Reproductive Medicine and Infertility, The New York Hospital-Cornell Medical Center 505, East, 70th Street, HT-326a, New York, NY 10021–4872, USA
Correspondence: 1To whom correspondence should be addressed
The purpose of this study was to assess the genetic status of abnormal zygotes following assisted fertilization. Dispermic, monopronucleated and digynic zygotes were allowed to cleave intact or after enucleation, and on the biopsied blastomeres, multiplex polymerase chain reaction and fluorescent in-situ hybridization were performed. It was found that the distal pronucleus was usually male in origin in dispermic embryos, and that the sex ratio was restored when they were enucleated; however, they became mosaic at metaphase and their genetic heterogeneity was not restored after enucleation. Monopronucleated zygotes derived from standard in-vitro insemination can be transferred to the patient, since they usually showed normal diploid complement in their cells. On the contrary, single-pronucleated zygotes derived from intracytoplasmic sperm injection were usually activated parthenogenetically, but not fertilized. Digynic embryos, unlike dispermic ones, had a very low incidence of mosaicism, and when present, such mosaicism originated at a later embryo division. Most of the digynic embryos were triploid, indicating that the first division was normal and bipolar; moreover, when the female pronucleus was removed, they became diploid and their genetic status was considered normal. The recognition and understanding of fertilization abnormalities allow the identification of methods leading to their avoidance or correction.
Key words: aneuploidy/abnormal fertilization/dispermic oocytes/digynic oocytes/mosaicism